Broadly, the invention relates to an apparatus for collecting samples of solid particles. More specifically, the apparatus is useful for sampling a stream of dry, free-flowing solids at a point between a classifier means and a packaging means.
Many chemical products are marketed in the form of dry, solid particles. An example of products in this category are ion exchange resins, which are used in home water conditioners to remove metal ions from the water. A commercially available ion exchange resin in marketed in the form of dry, solid, free flowing beads which range in size from about 20 mesh to 50 mesh.
In a typical manufacturing process the resin beads are discharged from a holding vessel onto a classifier screen. On the classifier screen the beads are separated into three general size ranges, for example, oversize beads undersize beads, and product size beads. From the classifier screen the product size beads are directed through a downwardly inclined delivery conduit and they drop into a hopper through an opening in the top of the hopper. When the hopper fills to a certain point, the solids are removed through a bottom opening and discharged into packaging containers.
To insure that the resin beads which make up the product are in the desired size range, it is necessary to periodically sample the solids being delivered into the hopper. Referring to the system described above, as the resin beads are carried into the storage hopper through the downwardly inclined conduit, the beads tend to segregate within the conduit. When segregation occurs, the larger (more dense) solids work toward the center of the material stream, and the smaller (less dense) solids will work outwardly and move along the periphery of the material stream. Because of this segregation problem, it is difficult to obtain a representative sample of the resin beads which are collected in the storage hopper. It is desirable, therefore, to collect a sample from the material stream at a point somewhere within the delivery conduit. In addition to collecting the sample in the delivery conduit, the sampling device must be capable of obtaining a full section of the material stream. Otherwise, the "product cut" will not represent the full size range of the particles being delivered into the storage hopper.
The conventional grabber type sampling devices are usually not satisfactory for this purpose. One reason is that there may be a limited amount of space between the classifier means and the top opening in the storage hopper. This creates a problem, in that the sample must be moved laterally from the point at which it is collected in the delivery conduit to a point at which it can be picked up. The lateral transfer of the sample, therefore, usually requires several pieces of equipment. This is undesirable from the standpoint of cost and the number of moving parts which are involved.